1. Field of the Invention
The present invention relates to an accumulator which is employed in various types of hydraulic devices for the absorption of pulsation or in hydropneumatic suspension systems for motor vehicles.
2. Description of the Related Art
Various types of accumulators adapted for their respective purposes have hitherto been put to practical use. For example, there is a type wherein a liquid chamber filled with an oil and a gas chamber containing a compressed gas are defined in the interior of a hollow housing. In a recently-developed accumulator of this type, a metallic bellows is employed to provide a partition between the liquid and gas chambers. The bellows is compressible or extensible in the axial direction of the housing, and one of the liquid and gas chambers is defined inside the bellows, with the other chamber defined outside of the bellows. The bellows is expanded or compressed in accordance with a variation in the pressure in either the liquid or gas chamber.
The inventors of the present invention developed an accumulator which is of a type employing a metallic bellows and which is provided with a self-seal mechanism for preventing the bellows from being deformed beyond an allowable extent when the gas chamber is charged with a gas.
In this accumulator, an inner cylinder and a metallic bellows are arranged coaxial inside a housing, and the bellows partitions the interior of the housing into liquid and gas chambers. The accumulator has an internal flow port through which a liquid flows into or out of the liquid chamber when the bellows is compressed or expanded. The flow port can be opened or closed by the self-seal mechanism. The self-seal mechanism is made up of: a support seat having the flow port formed therein; and an elastic seal member formed of rubber or the like and arranged to face the support seat. If the bellows is deformed beyond a predetermined stroke when the gas chamber is charged with a gas, the seal member closes the flow port, with the result that a liquid is confined to a backup liquid chamber defined between the bellows and the inner cylinder. Since a liquid is substantially an incompressible fluid, the liquid confined to the backup liquid chamber uniformly supports the entire wall of the bellows. As a result, the bellows is prevented from being excessively deformed.
In the process of the development of the abovementioned accumulator, the inventors found out that the accumulator required improvement in the point below:
If the self-seal mechanism closes itself at the time of the gas introduction into the gas chamber, the seal member is pressed strongly against the support seat. In some cases, the seal member may cling to the support seat. If the seal member clings to the support seat, the seal member does not easily separate from the support member, even when a liquid is introduced from a hydraulic pump or the like into the interior of the housing after the gas introduction. Since, therefore, the self-seal mechanism does not smoothly change from the closed state to the open state, it does not have satisfactory responsiveness.